JP2004002141A - Lithium nickel manganese oxide, its manufacturing method and lithium-ion secondary cell using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide LiNi<SB>1/2+α</SB>Mn<SB>1/2-α</SB>O<SB>2</SB>which suppresses cation mixing between the 3a-3b sites significant in Li Ni Mn O and has excellent output under high load and to provide a method for manufacturing the same. <P>SOLUTION: The compound is a positive electrode active substance expressed by the general formula of Li<SB>1+x</SB>Ni<SB>1/2+α</SB>Mn<SB>1/2-α</SB>O<SB>2</SB>with x and α satisfying x≥0 and -0.05≤α≤0.05 and shows ≥1.15 ratio of diffraction peak intensities (003)/(104) on the (003) face and the (104) face in terms of the Miller indices hkl in the powder X-ray diffraction using Cu-Kα ray. The method for manufacturing the compound includes a process of mixing nickel manganese oxide having an illmenite structure with a lithium compound and a process of calcining the mixture at ≥750°C in an oxygen-containing atmosphere. <P>COPYRIGHT: (C)2004,JPO

Description

【表２】

【発明の効果】
本発明のリチウム−ニッケル−マンガン複合酸化物とその製造方法を用いることにより、Ｃａｔｉｏｎ　ｍｉｘｉｎｇを抑制し高負荷での出力特性を向上させたＬｉＮｉ_{０．５＋ α}Ｍｎ_{０．５ー α}Ｏ_２およびこれを用いたリチウムイオン二次電池を提供可能である。
【図面の簡単な説明】
【図１】本発明実施例１に従って得られたニッケル−マンガン複合水酸化物の粉末Ｘ線回折図を示す。
【図２】本発明実施例１に従って得られたＮｉＭｎＯ_３の粉末Ｘ線回折図を示す。
【図３】本発明実施例１に従って得られたＬｉ_１．０１Ｎｉ_０．５０Ｍｎ_０．５０Ｏ_２の粉末Ｘ線回折図を示す。
【図４】本発明実施例１に従って得られたＬｉ_１．０１Ｎｉ_０．５０Ｍｎ_０．５０Ｏ_２のＴＥＭ観察写真および結晶構造モデル図を示す。
【図５】本発明実施例２に従って測定したＬｉ_１．０２Ｎｉ_０．５０Ｍｎ_０．５０Ｏ_２の充放電サイクル特性図を示す。
【図６】本発明実施例３に従って得られたＮｉＭｎＯ_３の粉末Ｘ線回折図を示す。
【図７】本発明実施例４に従って得られたＬｉ_１．０１Ｎｉ_０．５０Ｍｎ_０．５０Ｏ_２の粉末Ｘ線回折図を示す。
【図８】本発明実施例５に従って得られたＬｉ_１．０１Ｎｉ_０．５０Ｍｎ_０．５０Ｏ_２の粉末Ｘ線回折図を示す。
【図９】本発明実施例６に従って得られたＬｉ_１．００Ｎｉ_０．５０Ｍｎ_０．５０Ｏ_２の粉末Ｘ線回折図を示す。
【図１０】本発明実施例７に従って得られたＬｉ_１．０４Ｎｉ_０．５０Ｍｎ_０．５０Ｏ_２の粉末Ｘ線回折図を示す。
【図１１】本発明実施例８に従って得られたＬｉ_１．１０Ｎｉ_０．５０Ｍｎ_０．５０Ｏ_２の粉末Ｘ線回折図を示す。
【図１２】本発明実施例９に従って得られたＬｉ_１．０１Ｎｉ_０．４９Ｍｎ_０．５１Ｏ_２の粉末Ｘ線回折図を示す。
【図１３】比較例１に従って得られたＬｉ_１．０１Ｎｉ_０．５０Ｍｎ_０．５０Ｏ_２の粉末Ｘ線回折図を示す。
【図１４】比較例２に従って得られたＬｉ_１．０１Ｎｉ_０．５０Ｍｎ_０．５０Ｏ_２の粉末Ｘ線回折図を示す。
【図１５】比較例３に従って得られたＬｉ_１．００Ｎｉ_０．５０Ｍｎ_０．５０Ｏ_２の粉末Ｘ線回折図を示す。
【図１６】比較例４に従って得られたＬｉ_０．９８Ｎｉ_０．５０Ｍｎ_０．５０Ｏ_２の粉末Ｘ線回折図を示す。
【図１７】比較例５に従って測定したＬｉ_１．０１Ｎｉ_０．５０Ｍｎ_０．５０Ｏ_２の充放電サイクル特性図を示す。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a lithium-nickel-manganese composite oxide used as a positive electrode active material for a secondary battery, a method for producing the same, and a lithium ion secondary battery using the same.
[0002]
[Prior art]
In recent years, the miniaturization and cordlessness of AV equipment, mobile phones, personal computers, and the like have been rapidly progressing.₂, @ LiNiO₂, LiMn₂O₄Etc. have been studied. However, none of these materials can be said to satisfy all of capacity, safety, and cost._0.5Mn_0.5O₂Li-Ni-Mn composite oxides such as described above are expected as materials satisfying high energy density, safety and cost. (For example, see Non-Patent Document 1)
Conventionally, synthesis of such a Li—Ni—Mn composite oxide includes NiO, MnO, LiOH.H₂A dry mixing method obtained by mixing powders such as O (for example, see Non-Patent Document 2) has been widely used. However, when the Mn content is high, the uniformity of atoms is insufficient, so that an impurity phase is contained and the crystallinity is low, so that sufficient electrochemical characteristics cannot be obtained.
[0003]
In addition, in a method using a wet slurry in which a powder of Mn oxide or the like and a Ni solution, a Li solution, etc. are mixed into a slurry and fired, improvement in crystallinity, electrochemical properties, etc. is not achieved as compared with the dry method. However, there are problems such as generation of corrosive gas such as nitrogen oxides.
[0004]
On the other hand, in the coprecipitation method, it is possible to improve the uniform dispersibility of constituent atoms by coprecipitating in the form of hydroxide, carbonate, oxalate, or the like. In the coprecipitate, the choice of the precursor is important because the crystal structure of the precursor greatly affects the reactivity with the lithium compound, and furthermore, the crystal structure of the Li—Ni—Mn composite oxide and battery performance. For example, as a method of obtaining a Li-Ni-Mn composite oxide, a method of directly obtaining a Li-Ni-Mn composite oxide from a nickel-manganese composite hydroxide and a lithium compound is disclosed. Due to the instability of the divalent hydroxides, operation in air may cause a problem with the uniformity of the precursor. (See, for example, Patent Document 1.) Therefore, selection of a Ni—Mn compound having a high uniform dispersibility of constituent atoms, a high reactivity with a lithium compound, and a crystal structure stable in the air, and its Ni—Mn There was an urgent need to establish a method for producing a Li-Ni-Mn compound using the compound.
[0005]
Conventionally, LiNi using a Ni—Mn composite hydroxide as a raw material_0.5Mn_0.5O₂It has been reported that firing at a high temperature of 1000 ° C. or more is desirable for the synthesis of, and there is a report that there is a problem in cycle life at 850 ° C. or less. (For example, see Patent Document 1 and Non-Patent Document 1) On the other hand, LiNiO₂Replaced with Mn_1-XMn_XO₂Although there is a report that a relatively low firing temperature of 600 to 800 ° C. is required, it is only when the Mn substitution rate is low and LiNiO₂There is a view that it is not preferable to synthesize a lithium-containing composite oxide based on the above at a high temperature of 800 ° C. or higher. (For example, see Patent Document 2)
[Patent Document 1]
JP-A-2002-42813 (pages 4 to 5, FIG. 10)
[Patent Document 2]
JP-A-8-171910 (page 2
Column)
[Non-patent document 1]
Kotsuki et al. Proceedings of the 41st Battery Symposium (2000) 460-461
[Non-patent document 2]
E. FIG. Rossen et al. Solid State Ionics 57 (1992) 311-318.
[0007]
[Problems to be solved by the invention]
The present invention aims at obtaining a positive electrode active material for a lithium ion secondary battery having sufficient crystallinity and excellent electrochemical characteristics, in particular, to provide LiNi having a high degree of crystal perfection and excellent output characteristics._0.5Mn_0.5O₂And the LiNi_0.5Mn_0.5O₂The present invention provides a method for producing a lithium-nickel-manganese compound by reacting a nickel-manganese oxide having an ilmenite structure with a lithium compound to obtain the compound.
[0008]
LiNi synthesized by the present inventors using a Ni-Mn composite hydroxide as a raw material_0.5Mn_{0 . 5}O₂As a result of examining the correlation between the sintering temperature of the material and the physical properties and electrochemical properties of the material, it was found that Ni in the Li layer in the temperature range of 950 ° C. or higher.²⁺Movement, that is, Cation mixing between the 3a and 3b sites became apparent, and it became clear that the output characteristics under a high load condition were significantly reduced. Therefore, LiNi using Ni—Mn composite hydroxide as a raw material_0.5Mn_0.5O₂LiNi with reduced Cation mixing and improved output characteristics under high load_0.5Mn_0.5O₂And the establishment of its manufacturing method was urgently needed.
[0009]
At a high temperature such as 1000 ° C., the furnace material is significantly consumed, and the evaporation of lithium becomes remarkable, so that the composition tends to vary. On the other hand, conventional LiCoO₂And LiMn₂O₄Firing at a relatively low temperature, such as 800 to 900 ° C., which is found in the synthesis of, for example, has a great merit in production as compared with high-temperature firing. Therefore, LiNi having the crystal perfection and maintaining high load output characteristics is obtained._0.5Mn_0.5O₂There has been a demand for a production method capable of synthesizing at low temperature.
[0010]
[Means for Solving the Problems]
In order to solve the above problems, the lithium-nickel-manganese composite oxide of the present invention has a general formula Li_{1 + X}Ni_{1/2 + α}Mn_{1 / 2- α}O₂The X value in the formula represented by X ≧ 0, the α value is −0.05 ≦ α ≦ 0.05, and the (104) plane at the Miller index hkl where the particles of the composite oxide are hexagonal. The ratio of the diffraction peak intensity at the (003) plane and the (104) plane in the Miller index hkl of the powder X-ray diffraction using Cu-Kα ray is contained. 003) / (104) is 1.15 or more. Further, the average valence of nickel and manganese of the lithium-nickel-manganese composite oxide measured by an iodine titration method is 3.0 or more and 3.1 or less.
[0011]
Further, the production method is characterized by comprising a step of mixing an ilmenite type nickel-manganese oxide and a lithium compound, and a step of firing the mixture at 750 ° C. or more in an oxygen-containing atmosphere.
[0012]
[Action]
Hereinafter, the present invention will be described in detail.
[0013]
The lithium-nickel-manganese composite oxide of the present invention has the general formula Li_{1 + X}Ni_{1/2 + Α}Mn_{1 / 2- α}O₂It is represented by Here, when X <0, X ≧ 0 is indispensable because a by-product phase tends to be generated and Cation mixing becomes remarkable, and preferably 0.01 ≦ X ≦ 0.10. Excessive increase in X value causes Ni²⁺Ni for³⁺Increases, leading to a decrease in electrochemical capacity, which is inconvenient. The α value is −0.05 ≦ α ≦ 0.05, preferably α = 0. If the α value exceeds 0.05, Ni²⁺Ni for³⁺Increase the charge-discharge cycle characteristics. If α is less than -0.05, a single phase having a layered rock salt structure cannot be obtained.
[0014]
In addition, the lithium-nickel-manganese composite oxide of the present invention has a diffraction peak intensity ratio (003) / (003) / (104) plane at a Miller index hkl of powder X-ray diffraction using Cu-Kα ray. (104) is 1.15 or more. Here, the diffraction peak intensity ratio is an index of Cation mixing, and when the intensity ratio is high, the crystal perfection with a developed layer structure is high, and when the intensity ratio is low, the layer structure is disordered due to Cation mixing. (Eg, Ohzuku et al., J. Electrochem. @Soc., @ 140, @No. 7, (1993) 1862-1870). In the present compound, the ratio of the diffraction peak intensity at which the cation mixing does not become apparent and the output under a high load is maintained is 1.15 or more.
[0015]
In the lithium-nickel-manganese composite oxide of the present invention, the average valence of nickel and manganese measured by an iodine titration method is 3.0 or more and 3.1 or less. If the average valence is out of this range, the formation of a by-product phase becomes apparent and the battery capacity is reduced, which is not preferable.
[0016]
Further, the lithium-nickel-manganese composite oxide of the present invention is a FE-TEM which is a twin particle or a multiple twin particle having a (104) plane as a twin plane at a Miller index hkl assigned to a hexagonal system. And electron diffraction. Such a structure is not peculiar to layered rock salt compounds in general, but is characteristic of the present invention.
[0017]
The method for producing a positive electrode active material for a lithium ion secondary battery according to the present invention includes a step of mixing an ilmenite structure type nickel manganese oxide and a lithium compound, and a step of firing the mixture at 750 ° C. or more in an oxygen atmosphere. It is characterized by. By these operations, the positive electrode active material Li having the diffraction peak intensity ratio (003) / (104) of 1.15 or more is obtained._{1 + X}Ni_{1/2 + α}Mn_{1 / 2- α}O₂Is obtained. It is essential that uniformity at the atomic level is maintained by the coprecipitation method, and an operation such as a powder mixing method cannot provide a material having high crystal perfection and good electrochemical characteristics. When the Ni—Mn composite hydroxide is used as a raw material, firing at 750 ° C. or more and 950 ° C. or less in an oxygen-containing atmosphere is the most important condition for suppressing the cation mixing. At this time, as the lithium compound, hydroxide, acetate, carbonate, oxalate, nitrate, chloride, sulfate and the like can be used. In this case, it is desirable to use a hydroxide having a low decomposition temperature and generating no corrosive gas.
[0018]
The nickel manganese oxide used in the present invention is preferably of an ilmenite structure because of its high reactivity with lithium compounds. The ilmenite nickel-manganese oxide has the chemical formula NiMnO₃It is represented by Ilmenite structure is FeTiO₃And has a layered structure. The atomic ratio of Ni / Mn is preferably close to 1, and usually becomes an oxygen-deficient type. As a method for producing a nickel-manganese oxide having an ilmenite structure, synthesis under high pressure is often found. For example, as shown in Journal of Alloys and Compounds, {196} (1993) 75-79 Synthesis under normal pressure using a coprecipitation method using salt and oxalic acid is also possible.
[0019]
Also, the general formula Ni_{1/2 + α}Mn_{1 / 2- α}(OH)_y(COO)_z・ NH₂The nickel-manganese compound represented by O (y + z = 2, 0.5 ≦ z ≦ 1.5, α is the same as described above, and n ≧ 0) is fired at 550 ° C. or higher and lower than 800 ° C. in an oxygen atmosphere. can get.
[0020]
Ni_{1/2 + α}Mn_{1 / 2- α}(OH)_y(COO)_z・ NH₂When O is fired in a stream of air, an ilmenite structure can be obtained at 550 ° C. or higher and lower than 800 ° C.
[0021]
The ilmenite structure type nickel-manganese oxide can also be obtained by firing a nickel-manganese composite hydroxide. In this case, the nickel-manganese composite hydroxide is preferably in a uniform crystal phase in which nickel hydroxide and manganese hydroxide are dissolved. Usually, NiSO is used to prepare a nickel-manganese composite hydroxide.₄, Ni (NO₃)₂, Ni (CH₃COO)₂Nickel salts and MnSO₄, Mn (NO₃)₂, Mn (CH₃COO)₂It can be prepared by a hydroxide coprecipitation method using a manganese salt as a raw material. However, since the obtained composite hydroxide is unstable in divalent manganese hydroxide, it is oxidized by oxygen in the air during the operation and becomes Mn.₃O₄It is difficult to obtain a nickel-manganese composite hydroxide having a uniform crystal phase by-producing such oxides. Therefore, in order to prepare a nickel-manganese composite hydroxide having a stable and uniform crystal phase in air, it is necessary to prepare a nickel-manganese composite hydroxide in a uniform state in which nickel hydroxide and manganese hydroxide are dissolved. It is essential to oxidize the manganese therein to a stable trivalent or higher valent state with an oxidizing agent such as hydrogen peroxide. In this case, the average oxidation number of nickel and manganese is 2.5 or more when nickel is 2 or more and manganese is 3 or more.
[0022]
Oxidation with an oxidizing agent such as hydrogen peroxide is different from ordinary oxidation with air, etc., in that manganese hydroxide is converted to topotactic (without changing the structure) and stable manganese hydroxide such as β-manganese oxyhydroxide (β-MnOOH). It is considered that there is an effect of oxidizing to a state higher than the valence. Since β-manganese oxyhydroxide has a crystal structure very close to nickel hydroxide, it is considered that a uniform solid solution state is easily maintained and the composite hydroxide is stabilized.
[0023]
The oxidizing method using the oxidizing agent is not particularly limited. For example, the nickel-manganese composite hydroxide obtained by co-precipitation can be oxidized by being directly introduced into an alkaline aqueous solution containing an oxidizing agent such as hydrogen peroxide. . When co-precipitating the nickel-manganese composite hydroxide, a complexing agent such as ammonia which is added for improving the crystallinity of the nickel hydroxide may be added. By firing the nickel-manganese compound thus obtained in an oxygen-containing atmosphere, a nickel-manganese oxide having an ilmenite structure can be obtained. At this time, the ilmenite structure can be obtained in a range of about 300 ° C. or more and less than 800 ° C., but a low-crystalline one fired at a low temperature of 300 to 500 ° C. is desirable because of its high reactivity with a lithium compound.
[0024]
As a method of mixing the ilmenite structure type nickel manganese oxide and the lithium compound, in addition to the dry mixing method, a lithium slurry is dissolved in water or alcohol or the like to impregnate the nickel-manganese compound, and then the wet slurry is dried and fired. The method used is also effective. The slurry may be sprayed and dried by a spray. In addition, an oxygen atmosphere is essential for the firing atmosphere. If calcination is performed in an oxygen-free atmosphere such as nitrogen or argon, the desired product cannot be obtained because reduction occurs. Here, the aerobic atmosphere refers to an atmosphere having a higher oxygen partial pressure than air, such as air or pure oxygen.
[0025]
【Example】
Hereinafter, the present invention will be described with reference to specific examples.
[0026]
Example 1
450 ml of an aqueous solution in which 0.20 mol of nickel sulfate and 0.20 mol of manganese sulfate are dissolved and 450 ml of an aqueous solution in which 0.80 mol of sodium hydroxide are dissolved are stirred into 800 ml of a 1.6 mol / L aqueous ammonium solution while performing nitrogen bubbling. After the dropwise addition at the same time, the mixture was stirred and mixed at 25 ° C. overnight. Thereafter, while stirring 1.5 L of pure water, 50 ml of a 1.6 mol / L ammonium aqueous solution, 100 ml of 35% hydrogen peroxide solution and 100 ml of the obtained nickel-manganese coprecipitated slurry were added in the above order, and further 3 parts were added. Stirring was performed for hours. Thereafter, the precipitate was separated by filtration and dried at 80 ° C. overnight.
[0027]
The average oxidation number of nickel-manganese of the nickel-manganese composite hydroxide thus obtained was determined by iodometric titration, and as a result, the average oxidation number was 2.71. The X-ray diffraction pattern is shown in FIG. As shown in FIG. 1, Ni (OH)₂, Β-MnOOH. Thereafter, the nickel-manganese composite hydroxide was calcined at 400 ° C. in an air stream for 2 hours. As a result of chemical analysis of the obtained oxide by ICP, the composition was NiMnO.₃It was represented by The X-ray diffraction pattern of the oxide showed an ilmenite structure as shown in FIG.
[0028]
In addition, the ilmenite nickel-manganese oxide and lithium hydroxide monohydrate were mixed in an automatic mortar for 1 hour so that lithium atom / (nickel atom + manganese atom) (molar ratio) was 1.01. . The obtained mixture was calcined at 750 ° C. for 12 hours in an air stream to obtain a Li—Ni—Mn composite oxide. As a result of ICP composition analysis, Li_1.01Ni_0.50Mn_0.50O₂Met. The X-ray diffraction pattern was as shown in FIG. 3 and showed R3m containing no by-product phase or its analogous structure. Here, the diffraction peak intensity ratio (003) / (104) on the (003) plane and the (104) plane at the Miller index hkl was 1.20.
[0029]
The Li_1.01Ni_0.50Mn_0.50O₂Was measured for (Ni + Mn) average valence by iodometric titration. Iodometric titration is described in Dyer et al. American Chem Soc. , 76 (1954) 1499-1503.
[0030]
The iodine titration method utilizes the property that iodine is quantitatively released when an excessive amount of iodide ion is added to a strong oxidizing agent, and is a method of titrating and quantifying the free iodine with thiosulfate. After dissolving 0.3 g of a sample and 3.0 g of potassium iodide in 50 cc of 6 N HCl under light shielding, 200 cc of 1 N NaOH was added. After adding 1 cc of starch solution thereto, 0.1N-Na₂S₂O₃Was titrated. In addition, a blank measurement was performed in a system containing no sample, and the appropriate amount was corrected. As a result, the (Ni + Mn) average valence was 3.054.
[0031]
Next, the Li_1.01Ni_0.50Mn_0.50O₂Was observed by TEM. The sample was ultrasonically dispersed in ethanol without pulverization, and the suspension was dropped on a microgrid and collected to obtain a microscopic sample. A JEOL @ JEM-2010F field emission type 200 kV-TEM was used. FIG. 4 shows a lattice image of the domain boundary. The lattice fringes corresponding to the (003) plane spacing form an angle of about 110 °, and the c-axes of the two domains form an angle of about 70 ° with each other. The domain boundaries are not clear, and the two domains are intertwined with each other, and a portion overlapping in the direction of incidence of the electron beam appears as moire-like cross lattice fringes. However, the domain boundary is substantially parallel to the (104) plane. An ideal domain boundary model in which the (104) plane in FIG. 4 is a twin plane is shown. As described above, the twin or multi-twin particle structure having the (104) plane as the twin plane at the Miller index hkl assigned to the hexagonal crystal is not peculiar to the layered rock salt compound in general, and is characteristic of the present invention. It is something.
[0032]
Further, this was mixed as a positive electrode material of a battery at a ratio of 2: 1 by weight of a mixture of a conductive agent, polytetrafluoroethylene and acetylene black (trade name: TAB-2), and 1 ton / cm²After being formed into a pellet shape on a mesh (made of SUS316) at a pressure of 5 ° C., it was dried at 150 ° C. under reduced pressure to prepare a positive electrode for a battery. 1 mol / dm. Of lithium hexafluorophosphate in a mixed solvent of propylene carbonate and diethyl carbonate, and a negative electrode composed of the obtained battery positive electrode, a metal lithium foil (0.2 mm thick),³A battery was constructed using an electrolytic solution dissolved at a concentration of. Using the battery thus manufactured, the battery was charged and discharged at 23 ° C. with a constant current and a battery voltage of 4.3 V to 2.5 V. Charging is 0.4mA · cm^-2And discharge is 0.4 mA · cm^-2And 2.5 mA · cm^-2At two constant currents. Change the high rate discharge ratio to the discharge capacity ratio (2.5 mA^-2/0.4mA·cm^-2). As a result, the initial discharge capacity (0.4 mA · cm^-2) 147 mAh / g, high rate discharge ratio: 91.9%.
[0033]
Example 2
Li synthesized at 750 ° C. described in Example 1_1.01Ni_0.50Mn_0.50O₂, A charge / discharge cycle test was performed at 0.4 mA · cm as in Example 1.^-2Up to 30 cycles. FIG. 5 shows the charge-discharge cycle characteristics. LiNi obtained by the positive electrode material and the manufacturing method of the present invention_0.5Mn_0.5O₂Showed almost no deterioration even at a low temperature of 750 ° C.
[0034]
Example 3
Next, a nickel-manganese composite hydroxide was prepared in the same manner as in Example 1, and calcined at 650 ° C. in an air stream for 2 hours. As a result of chemical analysis of the obtained oxide by ICP, the composition was NiMnO.₃It was represented by The X-ray diffraction pattern of the oxide showed an ilmenite structure having higher crystallinity than that of Example 1 as shown in FIG. Further, the ilmenite nickel-manganese oxide and lithium hydroxide monohydrate were mixed in an automatic mortar for 1 hour so that lithium atom / (nickel atom + manganese atom) (molar ratio) was 1.01. . The obtained mixture was calcined at 750 ° C. for 12 hours in an air stream to obtain a Li—Ni—Mn composite oxide. As a result of ICP composition analysis, Li_1.01Ni_0.50Mn_0.50O₂Met. The Li_1.01Ni_0.50Mn_0.50O₂As a result of the same battery evaluation test as in Example 1, the initial discharge capacity (0.4 mA · cm^-2) Was 140.0 mAh / g, which was lower than that of Example 1. Therefore, LiNi with high battery performance_0.5Mn_0.5O₂In order to obtain, the crystallinity of the ilmenite structure needs to be low, and the firing temperature of the nickel-manganese composite hydroxide is desirably 300 to 500 ° C.
[0035]
Example 4
The preparation was performed in the same manner as in Example 1 except that the firing temperature in the lithiation was set to 900 ° C. As a result of ICP composition analysis, Li_1.01Ni_0.50Mn_0.50O₂Met. The X-ray diffraction pattern was as shown in FIG. 7 and showed R3m or its analogous structure. The diffraction peak intensity ratio (003) / (104) on the (003) plane and the (104) plane at the Miller index hkl was 1.19, and the average valence measurement of (Ni + Mn) by iodometric titration was 3.072. Met.
[0036]
Further, as a result of performing the same battery evaluation test as in Example 1, the initial discharge capacity (0.4 mA · cm^-2) 150.4 mAh / g, high rate discharge ratio: 89.9%.
[0037]
Example 5
The preparation was carried out in the same manner as in Example 1 except that the firing temperature in the lithiation was 925 ° C. As a result of ICP composition analysis, Li_1.01Ni_0.50Mn_0.50O₂Met. The X-ray diffraction pattern was as shown in FIG. 8 and showed R3m or its analogous structure. The diffraction peak intensity ratio (003) / (104) on the (003) plane and the (104) plane at the Miller index hkl was 1.21, and the (Ni + Mn) average valence measurement by iodometric titration was 3.097. Met.
[0038]
Further, as a result of performing the same battery evaluation test as in Example 1, the initial discharge capacity (0.4 mA · cm^-2) 147.0 mAh / g and a high rate discharge ratio of 89.0%.
[0039]
Example 6
The preparation was performed in the same manner as in Example 1 except that the firing temperature in the lithiation was 950 ° C. As a result of ICP composition analysis, Li_1.00Ni_0.50Mn_0.50O₂Met. The X-ray diffraction pattern was as shown in FIG. 9 and showed R3m or its analogous structure. The diffraction peak intensity ratio (003) / (104) on the (003) plane and the (104) plane at the Miller index hkl was 1.16, and the average valence measurement of (Ni + Mn) by iodometric titration was 3.087. Met.
[0040]
Further, as a result of performing the same battery evaluation test as in Example 1, the initial discharge capacity (0.4 mA · cm^-2) 147.4 mAh / g and a high rate discharge ratio of 87.5%.
[0041]
Example 7
A nickel-manganese oxide and lithium hydroxide monohydrate were mixed such that lithium atom / (nickel atom + manganese atom) (molar ratio) was 1.05, and the firing temperature in Li conversion was 900 ° C. Except for the above, it was prepared in the same manner as in Example 1. As a result of ICP composition analysis, Li_1.04Ni_0.50Mn_0.50O₂Met. The X-ray diffraction pattern was as shown in FIG. 10 and showed R3m or its analogous structure. The diffraction peak intensity ratio (003) / (104) on the (003) plane and the (104) plane at the Miller index hkl was 1.24, and the (Ni + Mn) average valence measurement by iodometric titration was 3.080. Met.
[0042]
Further, as a result of performing the same battery evaluation test as in Example 1, the initial discharge capacity (0.4 mA · cm^-2) 150.1 mAh / g, high rate discharge ratio: 89.2%.
[0043]
Example 8
A nickel-manganese oxide and lithium hydroxide monohydrate were mixed such that a lithium atom / (nickel atom + manganese atom) (molar ratio) was 1.11 and the firing temperature in Li conversion was 900 ° C. Except for the above, it was prepared in the same manner as in Example 1. As a result of ICP composition analysis, Li_1.10Ni_0.50Mn_0.50O₂Met. The X-ray diffraction pattern was as shown in FIG. 11, and showed R3m or its analogous structure. Here, the diffraction peak intensity ratio (003) / (104) on the (003) plane and the (104) plane at the Miller index hkl was 1.33, and (Ni + Mn) average valence measurement by an iodometric titration method revealed that 0.091.
[0044]
Further, as a result of performing the same battery evaluation test as in Example 1, the initial discharge capacity (0.4 mA · cm^-2) 139.5 mAh / g, high rate discharge ratio: 94.8%.
[0045]
Example 9
1.0 L of an aqueous 0.50 mol / L ammonium oxalate solution was added to 1.0 L of an aqueous solution in which 0.50 mol of nickel nitrate and 0.50 mol of manganese nitrate were dissolved, and the mixture was stirred and mixed at 25 ° C. for 1 day. Thereafter, the precipitate was separated by filtration and dried at 60 ° C. for 1 day. The composition of the precipitate thus obtained is Ni_0.49Mn_0.51(OH)_1.0(COO)_1.0・ 0.05H₂It was represented by O. Thereafter, the precipitate was calcined at 650 ° C. in an air stream for 12 hours. As a result of chemical analysis of the obtained oxide by ICP, the composition was Ni_0.49Mn_0.51O_1.5It was represented by The X-ray diffraction pattern of the oxide showed an ilmenite structure.
[0046]
The Ni_0.49Mn_0.51O_1.5Was impregnated with a lithium hydroxide aqueous solution, and calcined at 1000 ° C. for 10 hours in an air stream to obtain a Li—Ni—Mn composite oxide. As a result of ICP analysis, Li_1.01Ni_0.49Mn_0.51O₂It became. The Li_1.01Ni_0.49Mn_0.51O₂X-ray diffraction pattern is shown in FIG. As shown in FIG. 12, R3m containing no impurity phase or its related structure is shown. The diffraction peak intensity ratio (003) / (104) at the (003) plane and the (104) plane at the Miller index hkl was 1.18, and the (Ni + Mn) average valence measurement by iodometric titration was 3.020. Met.
[0047]
Further, as a result of performing the same battery evaluation test as in Example 1, the initial discharge capacity (0.4 mA · cm^-2) 140.4 mAh / g, high rate discharge ratio 90.9%.
[0048]
Example 10
1.0 L of a 0.5 mol / L aqueous solution of ammonium oxalate was added to 1.0 L of a mixed aqueous solution of 0.5 mol / L manganese nitrate and 0.5 mol / L nickel nitrate, followed by stirring and mixing at 25 ° C. for 1 day. . Thereafter, the precipitate was separated by filtration and dried at 60 ° C. for 1 day. The composition of the precipitate thus obtained is Ni_0.50Mn_0.50(OH)_1.0(COO)_1.0・ 0.05H₂It was represented by O. The precipitate was calcined at 500, 550, 600, 650, 700, 750, 800 and 850 ° C. for 12 hours in an air stream, and the X-ray diffraction pattern was examined. As a result, the firing temperature of the precipitate from which the ilmenite structure was obtained was in the range of 550 ° C. or more and less than 800 ° C.
[0049]
Example 11
To 1.0 L of an aqueous solution in which 0.50 mol of nickel sulfate and 0.50 mol of manganese sulfate were dissolved, 1.0 L of a 0.50 mol / L aqueous solution of ammonium oxalate was added, followed by stirring and mixing at 70 ° C. for 1 day. Thereafter, the precipitate was separated by filtration and dried at 60 ° C. for 1 day. The composition of the precipitate thus obtained is Ni_0.51Mn_0.49(OH)_1.0(COO)_1.0It was represented by Thereafter, the precipitate was calcined at 650 ° C. in an air stream for 12 hours. As a result of chemical analysis of the obtained oxide by ICP, the composition was Ni_0.51Mn_0.49O_1.5It was represented by The X-ray diffraction pattern of the oxide showed an ilmenite structure similar to that shown in FIG.
[0050]
The Ni_0.51Mn_0.49O_1.5Is impregnated with a 1.0 mol / L aqueous solution of lithium acetate so that the ratio of lithium atom / (nickel atom + manganese atom) (molar ratio) becomes 1.00, and calcined at 900 ° C. for 40 hours in an oxygen stream to obtain Li—Ni. -Mn composite oxide was obtained. As a result of ICP analysis, Li_1.00Ni_0.51Mn_0.49O₂The X-ray diffraction pattern showed R3m or an analogous structure thereof containing no impurity phase as in FIG. The battery test described in Example 1 showed an initial discharge capacity of about 140 mAh / g.
[0051]
Example 12
100 ml of an aqueous solution in which 0.20 mol of oxalic acid was dissolved was added to 400 ml of a 4 wt% acetic acid solution in which 0.10 mol of nickel acetate and 0.10 mol of manganese acetate were dissolved, and the mixture was boiled for 10 minutes and mixed with stirring. Thereafter, the precipitate was separated by filtration and dried at 60 ° C. for 1 day. The composition of the precipitate thus obtained is Ni_0.52Mn_0.48(OH)_1.0(COO)_1.0・ 0.07H₂It was represented by O. Thereafter, the precipitate was calcined at 650 ° C. in an air stream for 12 hours. As a result of chemical analysis of the obtained oxide by ICP, the composition was Ni_0.52Mn_0.48O_1.5It was represented by The X-ray diffraction pattern of the oxide showed an ilmenite structure similar to that shown in FIG.
[0052]
The Ni_0.52Mn_0.48O_1.5Is impregnated with a 1.0 mol / L aqueous solution of lithium acetate so that the lithium atom / (nickel atom + manganese atom) (molar ratio) becomes 1.05, and calcined at 1050 ° C. for 5 hours in an air stream to obtain Li-Ni -Mn composite oxide was obtained. As a result of ICP analysis, Li_1.05Ni_0.52Mn_0.48O₂The X-ray diffraction pattern showed R3m or an analogous structure thereof containing no impurity phase as in FIG. In addition, as a result of performing the battery test described in Example 1, the battery exhibited an initial discharge capacity of about 145 mAh / g.
[0053]
Example 13
1.0 L of a 0.50 mol / L aqueous solution of ammonium oxalate was added to 1.0 L of an aqueous solution in which 0.50 mol of nickel acetate and 0.50 mol of manganese acetate were dissolved, and the mixture was stirred and mixed at 70 ° C. for 1 day. Thereafter, the precipitate was separated by filtration and dried at 60 ° C. for 1 day. The composition of the precipitate thus obtained is Ni_0.51Mn_0.49(OH)_1.0(COO)_1.0・ 0.08H₂It was represented by O. Thereafter, the precipitate was calcined at 650 ° C. in an air stream for 12 hours. As a result of chemical analysis of the obtained oxide by ICP, the composition was Ni_0.51Mn_0.49O_1.5It was represented by The X-ray diffraction pattern of the oxide showed an ilmenite structure similar to that shown in FIG.
[0054]
The Ni_0.51Mn_0.49O_1.5Is impregnated with a 1.0 mol / L aqueous lithium acetate solution such that the lithium atom / (nickel atom + manganese atom) (molar ratio) becomes 1.00, and calcined at 1000 ° C. for 12 hours in an air stream to obtain Li—Ni. -Mn composite oxide was obtained. As a result of ICP analysis, Li_1.00Ni_0.51Mn_0.49O₂The X-ray diffraction pattern showed R3m or an analogous structure thereof containing no impurity phase as in FIG. As a result of the battery test described in Example 1, the battery showed an initial discharge capacity of about 143 mAh / g.
[0055]
Example 14
The nickel-manganese composite hydroxide obtained in Example 1 was calcined at 600 ° C. in an air stream for 3 hours. As a result of chemical analysis of the obtained oxide by ICP, the composition was NiMnO.₃It was represented by The X-ray diffraction pattern of the oxide showed an ilmenite structure similar to that shown in FIG.
[0056]
Also, after impregnating the ilmenite structure nickel-manganese oxide with a 1.0 mol / L aqueous solution of lithium hydroxide so that the ratio of lithium atom / (nickel atom + manganese atom) (molar ratio) becomes 1.01, the mixture was exposed to an air stream. Calcination was performed at 1000 ° C. for 10 hours to obtain a Li—Ni—Mn composite oxide. As a result of ICP analysis, Li_1.00Ni_0.50Mn_{0. 50}O₂The X-ray diffraction pattern showed R3m containing no by-product phase as shown in FIG. 9 or an analogous structure thereof. In addition, as a result of performing the battery test described in Example 1, the battery exhibited an initial discharge capacity of about 154 mAh / g.
[0057]
Comparative Example 1
The preparation was carried out in the same manner as in Example 1 except that the firing temperature in the lithiation was 975 ° C. As a result of ICP composition analysis, Li_1.01Ni_0.50Mn_0.50O₂Met. The X-ray diffraction pattern was as shown in FIG. 13 and showed R3m or its analogous structure. The diffraction peak intensity ratio (003) / (104) on the (003) plane and the (104) plane at the Miller index hkl was 1.10, and the average valence measurement of (Ni + Mn) by iodometric titration was 3.088. Met.
[0058]
Further, as a result of performing the same battery evaluation test as in Example 1, the initial discharge capacity (0.4 mA · cm^-2) 139.8 mAh / g, high rate discharge ratio: 79.6%.
[0059]
Comparative Example 2
The preparation was carried out in the same manner as in Example 1 except that the firing temperature in the lithiation was changed to 1000 ° C. As a result of ICP composition analysis, Li_1.01Ni_0.50Mn_0.50O₂Met. The X-ray diffraction pattern was as shown in FIG. 14, and showed R3m or its analogous structure. The diffraction peak intensity ratio (003) / (104) on the (003) plane and the (104) plane at the Miller index hkl was 1.06, and (Ni + Mn) average valence measurement by iodometric titration was performed. 109.
[0060]
Further, as a result of performing the same battery evaluation test as in Example 1, the initial discharge capacity (0.4 mA · cm^-2) 133.9 mAh / g and a high rate discharge ratio of 75.7%.
[0061]
Comparative Example 3
The preparation was carried out in the same manner as in Example 1, except that the firing temperature in the lithiation was 1050 ° C. As a result of ICP composition analysis, Li_1.00Ni_0.50Mn_0.50O₂Met. The X-ray diffraction pattern was as shown in FIG. 15, and showed R3m or its analogous structure. The diffraction peak intensity ratio (003) / (104) on the (003) plane and the (104) plane at the Miller index hkl was 1.03, and the (Ni + Mn) average valence measurement by iodometric titration was 3.098. Met.
[0062]
Further, as a result of performing the same battery evaluation test as in Example 1, the initial discharge capacity (0.4 mA · cm^-2) 34.9 mAh / g, high rate discharge ratio: 33.0%.
[0063]
Comparative Example 4
Nickel-manganese oxide and lithium hydroxide monohydrate were mixed so that lithium atom / (nickel atom + manganese atom) (molar ratio) was 0.98, and the firing temperature in Li conversion was 900 ° C. Except for the above, it was prepared in the same manner as in Example 1. As a result of ICP composition analysis, Li_0.98Ni_0.50Mn_0.50O₂Met. The X-ray diffraction pattern is as shown in FIG.₂MnO₃Thus, a mixed phase containing a by-product phase was obtained. Further, when the (Ni + Mn) average valence was measured by an iodine titration method, it was 3.100.
[0064]
Further, as a result of performing the same battery evaluation test as in Example 1, the initial discharge capacity (0.4 mA · cm^-2) 42.89 mAh / g and a high rate discharge ratio of 23.8%.
[0065]
Comparative Example 5
Further, Li synthesized at 1000 ° C. described in Comparative Example 2_1.01Ni_0.50Mn_0.50O₂, A charge / discharge cycle test was performed at 0.4 mA · cm in the same manner as in Example 2.^-2Up to 30 cycles. FIG. 17 shows charge / discharge cycle characteristics. In comparison with the charge / discharge cycle characteristic diagram of FIG.
[0066]
Comparative Example 6
1.0 L of a 0.50 mol / L aqueous solution of ammonium oxalate was added to 1.0 L of an aqueous solution in which 0.50 mol of nickel nitrate and 0.50 mol of manganese nitrate were dissolved, and the mixture was stirred and mixed at 70 ° C. for 1 day. Thereafter, the precipitate was separated by filtration and dried at 60 ° C. for 1 day. Thereafter, the precipitate was calcined at 800 ° C. in an air stream for 12 hours. As a result of chemical analysis of the obtained oxide by ICP, the atomic ratio of Mn / Ni was 0.968. The X-ray diffraction pattern of the oxide showed a spinel structure.
[0067]
After mixing the oxide and lithium hydroxide monohydrate, the mixture was calcined at 1000 ° C. for 10 hours in an oxygen stream to obtain a Li—Ni—Mn composite oxide. As a result of ICP analysis, Li_1.01Ni_0.51Mn_0.49O₂The X-ray diffraction pattern showed R3m or an analogous structure thereof. However, as a result of the battery test described in Example 1, the initial discharge capacity was about 125 mAh / g.
[0068]
Comparative Example 7
1.0 L of a 0.50 mol / L aqueous solution of ammonium oxalate was added to 1.0 L of an aqueous solution in which 0.50 mol of nickel nitrate and 0.50 mol of manganese nitrate were dissolved, and the mixture was stirred and mixed at 70 ° C. for 1 day. Thereafter, the precipitate was separated by filtration and dried at 60 ° C. for 1 day. Thereafter, the precipitate was calcined at 400 ° C. in an air stream for 12 hours. As a result of chemical analysis of the obtained oxide by ICP, the atomic ratio of Mn / Ni was 0.968. The X-ray diffraction pattern of the oxide showed a spinel structure with low crystallinity.
[0069]
After mixing the oxide and lithium hydroxide monohydrate, the mixture was calcined at 1000 ° C. for 10 hours in an oxygen stream to obtain a Li—Ni—Mn composite oxide. As a result of ICP analysis, Li_1.01Ni_0.51Mn_0.49O₂The X-ray diffraction pattern showed R3m containing no impurity phase or its analogous structure. The battery test described in Example 1 showed that the initial discharge capacity was about 115 mAh / g.
[0070]
Comparative Example 8
As in Example 9, Ni having an ilmenite structure was used._0.49Mn_0.51O_1.5Was synthesized.
[0071]
After mixing the oxide and lithium hydroxide monohydrate so that the ratio of lithium atom / (nickel atom + manganese atom) (molar ratio) becomes 1.05, the mixture is fired in an oxygen stream at 1100 ° C. for 10 hours. Thus, a Li-Ni-Mn composite oxide was obtained. As a result of ICP analysis, Li_1.02Ni_0.49Mn_0.51O₂And the X-ray diffraction pattern showed R3m or its analogous structure. However, the battery test described in Example 1 showed a low initial discharge capacity of about 84 mAh / g.
[0072]
Comparative Example 9
As in Example 9, Ni having an ilmenite structure was used._0.49Mn_0.51O_1.5Was synthesized.
[0073]
After mixing the oxide with lithium hydroxide monohydrate, the mixture was calcined at 850 ° C. for 10 hours in an oxygen stream to obtain a Li—Ni—Mn composite oxide. As a result of ICP analysis, Li_1.01Ni_0.49Mn_0.51O₂Met. However, the X-ray diffraction pattern showed R3m or its analogous structure, but was relatively low crystalline. As a result of the battery test described in Example 1, the initial discharge capacity was about 99 mAh / g.
[0074]
Table 1 shows the X-ray diffraction peak intensity ratio (003) / (104) and the battery test results of Examples and Comparative Examples of the present invention. Here, when the raw material A is a Ni-Mn composite hydroxide as the raw material, the raw material B is_{1/2 + α}Mn_{1 / 2- α}(OH)_y(COO)_z・ NH₂The case where O was used is shown.
[0075]
Table 2 shows the average valencies of nickel and manganese in the lithium-nickel-manganese compounds of Examples of the present invention and Comparative Examples.
[0076]
[Table 1]

[Table 2]

【The invention's effect】
LiNi that suppresses cation mixing and improves output characteristics under high load by using the lithium-nickel-manganese composite oxide and the method for producing the same according to the present invention._{0.5+ α}Mn_{0.5- α}O₂And a lithium ion secondary battery using the same.
[Brief description of the drawings]
FIG. 1 shows a powder X-ray diffraction diagram of a nickel-manganese composite hydroxide obtained according to Example 1 of the present invention.
FIG. 2 shows a NiMnO obtained according to the invention Example 1.₃1 shows a powder X-ray diffraction pattern of the sample.
FIG. 3 shows Li obtained according to Example 1 of the present invention._1.01Ni_0.50Mn_0.50O₂1 shows a powder X-ray diffraction pattern of the sample.
FIG. 4 shows Li obtained according to Example 1 of the present invention._1.01Ni_0.50Mn_0.50O₂1 shows a TEM observation photograph and a crystal structure model diagram of FIG.
FIG. 5 shows Li measured according to Example 2 of the present invention._1.02Ni_0.50Mn_0.50O₂FIG. 3 shows a charge / discharge cycle characteristic diagram of FIG.
FIG. 6 shows NiMnO obtained according to Inventive Example 3₃1 shows a powder X-ray diffraction pattern of the sample.
FIG. 7 shows Li obtained according to Example 4 of the present invention._1.01Ni_0.50Mn_0.50O₂1 shows a powder X-ray diffraction pattern of the sample.
FIG. 8 shows Li obtained according to Example 5 of the present invention._1.01Ni_0.50Mn_0.50O₂1 shows a powder X-ray diffraction pattern of the sample.
FIG. 9 shows Li obtained according to Example 6 of the present invention._1.00Ni_0.50Mn_0.50O₂1 shows a powder X-ray diffraction pattern of the sample.
FIG. 10 shows Li obtained according to Example 7 of the present invention._1.04Ni_0.50Mn_0.50O₂1 shows a powder X-ray diffraction pattern of the sample.
FIG. 11 shows Li obtained according to Example 8 of the present invention._1.10Ni_0.50Mn_0.50O₂1 shows a powder X-ray diffraction pattern of the sample.
FIG. 12 shows Li obtained according to Example 9 of the present invention._1.01Ni_0.49Mn_0.51O₂1 shows a powder X-ray diffraction pattern of the sample.
FIG. 13 shows Li obtained according to Comparative Example 1._1.01Ni_0.50Mn_0.50O₂1 shows a powder X-ray diffraction pattern of the sample.
FIG. 14 shows Li obtained according to Comparative Example 2._1.01Ni_0.50Mn_0.50O₂1 shows a powder X-ray diffraction pattern of the sample.
FIG. 15 shows Li obtained according to Comparative Example 3._1.00Ni_0.50Mn_0.50O₂1 shows a powder X-ray diffraction pattern of the sample.
FIG. 16 shows Li obtained according to Comparative Example 4._0.98Ni_0.50Mn_0.50O₂1 shows a powder X-ray diffraction pattern of the sample.
FIG. 17 shows Li measured according to Comparative Example 5._1.01Ni_0.50Mn_0.50O₂FIG. 3 shows a charge / discharge cycle characteristic diagram of FIG.

Claims (13)

In the formula represented by the general formula Li _{1 + X} Ni _{1/2 + α} Mn _{1 / 2- α} O ₂ , lithium-nickel with the X value being X ≧ 0 and the α value being −0.05 ≦ α ≦ 0.05. A manganese composite oxide, wherein the particles of the composite oxide include twin particles having a (104) plane as a twin plane at a Miller index hkl assigned to a hexagonal crystal, and powder X using Cu-Kα radiation; The diffraction peak intensity ratio (003) / (104) on the (003) plane and the (104) plane at the mirror index hkl of the line diffraction is 1.15 or more, and 0.3 g of the lithium-nickel-manganese composite oxide And 3.0 g of potassium iodide are dissolved in 50 cc of 6 N HCl in a light-shielded state, 200 cc of 1 N NaOH and 1 cc of a starch solution are added, and titration is performed with 0.1 N Na ₂ S ₂ O _3. By law Lithium average valence of the measured nickel and manganese is 3.0 or more 3.1 or less - nickel - manganese composite oxide. Formula _{Li 1 + X Ni 1/2} + α Mn 1 / X value in the formula represented by the _2-alpha O ₂ is 0.01 ≦ X ≦ 0.10, the alpha value -0.05 ≦ α ≦ 0.05 The lithium-nickel-manganese composite oxide according to claim 1. The lithium-nickel according to claim 1 or 2, wherein a step of mixing the ilmenite structure-type nickel-manganese oxide and the lithium compound is performed, and the mixture is fired at a firing temperature of 750 ° C or more in an oxygen-containing atmosphere. -A method for producing a manganese composite oxide. 4. The process according to claim 3, wherein the ilmenite structure type nickel-manganese oxide is mixed with a lithium compound, and the mixture is fired at a firing temperature of 750 ° C. or more and 950 ° C. or less in an oxygen-containing atmosphere. A method for producing a manganese composite oxide. A nickel-manganese compound having an average oxidation number of 2.5 or more of nickel and manganese synthesized by oxidizing a nickel-manganese composite hydroxide by an ilmenite-structured nickel-manganese oxide is prepared in an aerobic atmosphere at 300 ° C or more and 800 or more. The method for producing a lithium-nickel-manganese composite oxide according to claim 4, which is an oxide obtained by calcining at a temperature lower than 0 ° C. The method for producing a lithium-nickel-manganese composite oxide according to claim 5, wherein the firing temperature is 300C or more and 500C or less. The method for producing a lithium-nickel-manganese composite oxide according to claim 5, wherein the nickel-manganese composite hydroxide is synthesized in the presence of a complexing agent. The method for producing a lithium-nickel-manganese composite oxide according to claim 7, wherein the complexing agent is ammonia. 4. The lithium-nickel according to claim 3, wherein the step of mixing the ilmenite structure type nickel-manganese oxide and the lithium compound is performed, and the mixture is fired at a firing temperature of 900 ° C. or more and 1050 ° C. or less in an oxygen atmosphere. A method for producing a manganese composite oxide. The ilmenite structure nickel-manganese oxide has a general formula Ni _{1/2 + α} Mn _{1 / 2- α} (OH) _y (COO) _z · nH ₂ O (y + z = 2, 0.5 ≦ z ≦ 1.5, The nickel-manganese oxide obtained by firing a nickel-manganese compound represented by an α value of −0.05 ≦ α ≦ 0.05, n ≧ 0) in an oxygen-containing atmosphere. A method for producing a lithium-nickel-manganese composite compound. The method for producing a lithium-nickel-manganese composite oxide according to claim 10, wherein the firing temperature is 550 ° C or higher and lower than 800 ° C. A positive electrode active material for a lithium ion secondary battery, comprising the lithium-nickel-manganese composite oxide according to claim 1. A lithium ion secondary battery using the positive electrode active material according to claim 12.

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